Archive for December 2009

Abstract: Nano-sized sulphur and oxidizers were synthesized by the ball mill method and the size was determined using a particle size analyzer. Pyrotechnic mixtures of compositions using five different oxidizers: potassium nitrate (KNO3), potassium perchlorate (KClO4), barium nitrate (Ba(NO3)2), strontium nitrate (Sr(NO3)2) and bismuth oxide (Bi2O3), in different particle sizes, mixed with sulphur (S), aluminium (Al) and boric acid (H3BO3), were used to produce sound producing cake-bomb firecrackers for analysis. A bulk density of 0.24–0.68 g cm−3 was maintained for homogeneity of the mixture. The sound level from newly formulated sound producing firecrackers (cake-bombs) showed a linear relationship with the weight of the mixture taken. Decreasing the particle size from micro to nano improves the efficiency of firecrackers using the oxidizers, KNO3, KClO4 but not for Ba(NO3)2, Sr(NO3)2., or Bi2O3. The analysis of safety characteristic data of thermal and mechanical sensitiveness indicates that the pyrotechnic mixture using the oxidizer KClO4 is highly sensitive to friction and impact. The limiting impact energy (LIE) of pyrotechnic compositions falls in the range of 2.55–4.51 J. LIE of nano materials was less compared to micro materials indicating that as the particle size decreases, the mixture is prone to hazards from impact. Thermal analysis indicates a high temperature for self propagating decomposition making the mixture thermally stable at room temperature.

Abstract: This work presents results of investigations towards the emission of chemical reaction products and sound pressure during an outdoor and an indoor firework display. Potentially harmful and toxic gases, and aerosols, were measured as well as sound pressures. Aerosols were measured with a Differential Mobility Analyzer (DMA) as well as a Laser Particle Counter. The focus was on particles with diameters between 11 nm and 20 μm. A transportable Fourier Transform Infrared (FTIR) spectroscopy detector registered the concentrations of emitted reaction gases, simultaneously. During the outdoor firework display, peak particle concentrations of >550 000 particles cm−3, equivalent to a mass concentration of approximately 3.95 mg m−3, were detected, revealing a concentration maximum at approximately 175 nm particle diameter. The time-averaged particle mass concentration did not exceed 1.58 mg m−3 over 15 minutes. Due to the large distances (110 m) to the firing points, no significant harmful or toxic gas concentrations were measured during the entire firework display. In contrast, concentrations of sulphur dioxide (SO2) rose after an indoor firework display in a large event hall. On two days, more than 23 000 particles cm−3 (which equates to a mass concentration of approximately 0.41 mg m−3) were detected when the hall ventilation was turned off, and more than 11 000 particles cm−3 (which equates to a mass concentration of approximately 1.18 mg m−3) when the hall ventilation was activated. Concentration maxima appeared at approximately 300 nm particle diameter. The time-averaged particle concentrations in this case did not exceed 0.56 mg m−3 (over 15 minutes).